1. Field of the Invention
This invention relates generally to magnetic heads in disk drives, and more particularly to improved methods of making magnetic write heads with side and trailing shield structures.
2. Description of the Related Art
A write head is typically combined with a magnetoresistive (MR) read head to form a merged MR head, certain elements of which are exposed at an air bearing surface (ABS). In conventional designs, the write head comprises first and second pole pieces connected at a back gap that is recessed from the ABS. The first and second pole pieces have first and second pole tips, respectively, which terminate at the ABS. An insulation stack, which comprises a plurality of insulation layers, is sandwiched between the first and second pole pieces, and a coil layer is embedded in the insulation stack. A processing circuit is connected to the coil layer for conducting write current through the coil layer which, in turn, induces write fields in the first and second pole pieces. A non-magnetic gap layer is sandwiched between the first and second pole tips. Write fields of the first and second pole tips at the ABS fringe across the gap layer. In a magnetic disk drive, a magnetic disk is rotated adjacent to, and a short distance (fly height) from, the ABS so that the write fields magnetize the disk along circular tracks. The written circular tracks then contain information in the form of magnetized segments with fields detectable by the MR read head.
An MR read head includes an MR sensor sandwiched between first and second non-magnetic gap layers, and located at the ABS. The first and second gap layers and the MR sensor are sandwiched between first and second shield layers. In a merged MR head, the second shield layer and the first pole piece are a common layer. The MR sensor detects magnetic fields from the circular tracks of the rotating disk by a change in resistance that corresponds to the strength of the fields. A sense current is conducted through the MR sensor, where changes in resistance cause voltage changes that are received by the processing circuitry as readback signals.
One or more merged MR heads may be employed in a magnetic disk drive for reading and writing information on circular tracks of a rotating disk. A merged MR head is mounted on a slider that is carried on a suspension. The suspension is mounted to an actuator which rotates the magnetic head to locations corresponding to desired tracks. As the disk rotates, an air layer (an “air bearing”) is generated between the rotating disk and an air bearing surface (ABS) of the slider. A force of the air bearing against the air bearing surface is opposed by an opposite loading force of the suspension, causing the magnetic head to be suspended a slight distance (flying height) from the surface of the disk.
As the lifetime of longitudinal magnetic recording to achieve higher a real density may have reached its limit, however, perpendicular magnetic recording has received renewed interest to extend to ultra-high density magnetic recording. Recent demonstrations have shown that excellent recording performance can be achieved at areal densities as high as 150 gigabit/in2 using a single pole recording head (SP) on perpendicular media with soft underlayers. Thus, SP with a leading edge tapering (LET) design may be suitable alternative for perpendicular magnetic recording. However, exploratory magnetic modeling and characterization on perpendicular head design suggest that higher a real density can be achieved by incorporating side and trailing shields into the single pole writer design (SPT). Improvements of the SPT design over the SP design can be explained by the Stoner-Wohlfarth model for a single particle.
FIG. 8 is a plot 800 of H-grain angle as a function of mean grain angle in the Stoner-Wohlfarth model for the SPT design. From plot 800, one can assess that for a distribution angle of grain angles, increasing the angle between H and mean grain angle decreases the distribution of switching fields by one-half to thereby increase the effective field by two times and reduce jitter. By effectively angling the write field, an SPT design can achieve a 4–5 dB media signal-to-noise advantage over writing with the trailing edge of an unshielded pole, increase dHy/dx of the write field, reduce partial erasure, and improve saturation. These features improve transition sharpness (linear resolution) and permit higher coercive field media (improved stability). These are preferred parameters for higher a real density targets.
Suitable methods are needed for fabricating such write heads with side and trailing shields. Although damascene techniques have been utilized in the fabrication of write head structures such as the write coil, the electroplated material (e.g. copper) is not an alloy and is non-magnetic. Damascene techniques also require a bath additive to suppress plating in particular desired areas.